Because American drivers have normalized always driving 10 mph (16 km/h) over the speed limit.

Cops won't pull you over or write tickets if you're not at least 15 mph over, we basically don't have speed cameras, everyone's trying to win the rat race and dehumanizing other cars around them, and it's not considered morally wrong (by most) to break that specific part of the law.

So a single vehicle obeying the law will quickly get a long line of tailgaters and tailgaters of tailgaters trying to "push" the vehicle to go faster.

They can suck it, I'm not late or in a hurry, and my ancient truck, steel bumper, and class 5 receiver hitch will not be badly harmed by your plastic grille. I get better gas mileage and have a longer stopping distance when I drive the limit, and I don't care if others are honking or riding my ass because they think I should drive faster.

> my ancient truck, steel bumper, and class 5 receiver hitch will not be badly harmed by your plastic grille

I've been rear-ended in my truck, and the receiver punched a nice hole right through the radiator of the guy who hit me. Definitely fucked his car up way more than it did my truck ... except man, that is definitely one of the hardest impacts I've ever felt in my body. I now appreciate how hard the head rests really are, despite looking a little soft. I think I'd rather have crumpled crumple zones and a new truck next time.